PHP mail not delivering mail

Pertinent PHP Settings:
SMTP: localhost
sendmail_from: None
sendmail_path: /usr/sbin/sendmail -t -i
Diagnostic Results:
No errors were returned while attempting to send the email. Check destination@email.dom shortly to confirm you've received the email. If you don't receive the email, try sending the test to a different address. If that fails, check your mail server's configuration.